The invention relates generally to tools for installing helical coil inserts into tapped holes and, more particularly, to such power installation tools having a punch for breaking off a tang of the helical coil insert.
Helical coil inserts are commonly installed into tapped holes of a workpiece so that threaded fasteners such as screws can be held more securely. These inserts are frequently used to improve the gripping of threaded fasteners made of relatively hard materials, such as various steel alloys, when installed in relatively soft parent materials, such as aluminum. Helical coil inserts typically include a diametrical tang used as a grip by a mandrel of the installation tool for screwing the helical coil insert into the tapped hole.
Helical coil inserts of this kind are usually installed by pre-winding them to reduce their diameter, and then rotatably threading them into a tapped hole. Once installed, the inserts expand from their contracted diameters and press radially outwardly against the walls defining the tapped holes, whereby the insert is securely held in place. Power tools for installing inserts are typically driven by an air motor and include a tubular body having a threaded bore extending along its axis and an opening at one end of the body for placing an insert in the bore. A mandrel is rotated by the motor within the threaded bore into engagement with the insert. Advancement of the mandrel forces the insert through a pre-winder, which reduces the insert""s diameter, and from there into a tapped hole in an adjacent workpiece.
Once the insert is installed at the correct depth in the bore of the workpiece, the mandrel is reversed until it is removed from the insert. In many instances, particularly if a through-going hole is lined with an insert, the tang must be removed after installation as otherwise it would interfere with a bolt engaging the insert. To facilitate removal of the tang, a notch is conventionally provided in the wire near the point where the diametrical tang joins the adjacent coil convolution. Thus, after using a conventional power tool to install the insert, the installer uses a second tool to break the tang at the notch.
This two-tool process is time consuming and inefficient, particularly when many bores must be lined with helical coil inserts, such as in a manufacturing setting. Great efficiencies and cost savings would be realized by combining and simplifying the helical coil insert installation and tang removal process.
A single tool for installing a helical coil insert in a tapped hole formed in a workpiece and removing a tang from a leading coil convolution simplifies the helical coil insert installation process. The power installation tool according to the invention includes a tubular body having a bore extending along its axis. A recess preferably provided at one end of the tubular body carries a helical coil insert in alignment with the bore. An opening in the tubular body allows access to the recess for placing the insert in the recess. A mandrel is coaxially disposed in the bore of the tubular body and is movable to engage and rotate the helical coil insert for installation. More specifically, a hook on the leading end of the mandrel engages a tang on the helical coil insert for winding the helical coil insert about the leading end of the mandrel prior to installation of the coil in the tapped hole of the workpiece. Further, the mandrel includes an axial bore that mounts a punch, which is movable axially to sever the tang from the helical coil insert upon full installation of the insert in the tapped hole of the workpiece. A motor rotates the mandrel to insert the helical coil insert a predetermined distance in the tapped hole. An air cylinder applies an axial force to the punch to move it from a retracted position to an extended position where it removes the tang.
Preferably, the air motor is offset axially from the tubular body and is connected to the mandrel by a gear train, whereby rotation of the motor shaft rotates the mandrel. It is preferred to include a drive sleeve in the tubular body for connecting the gear train to the mandrel.
The punch for removing the tang from the helical coil insert may include a hammer adapted to slide axially in the bore under force of air from the air cylinder to engage and move the punch to its extended position. Alternatively, a piston in the air cylinder is connected to the punch, whereby air acting on the piston in the cylinder causes the punch to slide axially in the bore to its extended position.